1. Field of the Invention
The present invention relates to a technique for repositioning bone portions for bone surgery, in particular for facial surgery, the technique being based on the use of customized implants and guides.
2. Description of the Related Technology
Some surgical interventions are intended to correct bone deformations, occurrences of disharmony or proportional defects of the face, or post-traumatic after-effects. These interventions use actions for repositioning, in an ideal location, some fragments of bone which have been separated from a base portion beforehand by a surgeon.
Such surgical interventions therefore comprise an osteotomy which is carried out in order to release one or more badly-positioned bone segments; for example, to move this or these bone segment(s), that is to say, to move it/them by way of translation and/or by rotation in order to be able to reposition it/them at their ideal location after this movement.
When all bone segments occupy a new ideal position, the surgeon fixes the bone segments to other adjacent bone portions of the patient using for one or more implants. These may comprise perforated implants, which may have different geometries, for example, in the form of I-shaped, L-shaped, T-shaped, X-shaped, H-shaped or Z-shaped plates, or more complex geometries. The implants are fixed to all the portions of bone to be joined in their correct relative positions using osteosynthesis screws which extend through their perforations.
It is then, in this way, possible to seek to restore the symmetry of the face or normal anthropometric relationships.
U.S. Pat. Nos. 5,690,631 and 6,221,075 describe such implants in the form of plates or trellises which are capable of allowing at least two bone portions to be joined and fixed to each other.
Amongst the various forms of surgery which affect the facial skeleton, it is possible to mention:                orthognathic surgery, the objective of which is to reposition dental bridges in relative comfortable positions, ensuring good engagement of the teeth; such an intervention involves a maxillary osteotomy if it is necessary to move the upper dental bridge, or a mandibular osteotomy if it is necessary to move the lower dental bridge, or a bi-maxillary osteotomy if it is advantageous to move segments of bone on the two jaws in order to also re-establish the normal proportions of a face,        genioplasty involving an operation on the chin of a patient for aesthetic matters (in order to correct an excessively protruding chin or in contrast a receding chin) or for functional matters, for example, allowing a patient to be able to move his lips into contact with each other without effort,        the correction of post-traumatic after-effects, for example, with regard to the zygomatic bone, following accidental impacts.        
A technique for producing a made-to-measure preformed implant is described in an International Patent Application published on 3 Nov. 2011 under the number WO 2011/136898. The technique therein comprises the production of a made-to-measure guide which is also pre-shaped and which serves to guide the drilling of some holes for the osteosynthesis screws and which also serves to guide an osteotomy.
A disadvantage of the aforementioned prior technique is that it is dependent on the quality of the osteotomy, or the resection operation, carried out by the surgeon.
An object of certain embodiments of the invention disclosed herein is to overcome such a disadvantage. For example, it is desired to have excellent connection of the first portion of the bone and the second portion of the bone, even if the osteotomy and/or the resection were to be imperfect, imprecise and even approximate.